US5390142A - Memory material and method for its manufacture - Google Patents
Memory material and method for its manufacture Download PDFInfo
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- US5390142A US5390142A US07/889,025 US88902592A US5390142A US 5390142 A US5390142 A US 5390142A US 88902592 A US88902592 A US 88902592A US 5390142 A US5390142 A US 5390142A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
- H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
- H01F10/12—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L28/00—Passive two-terminal components without a potential-jump or surface barrier for integrated circuits; Details thereof; Multistep manufacturing processes therefor
- H01L28/40—Capacitors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/14—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using thin-film elements
- G11C11/15—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using thin-film elements using multiple magnetic layers
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/90—Magnetic feature
Definitions
- Computer technology requires memories having large storage capacity and high speed.
- a semiconductor memory is employed as high-speed primary memory and magnetic disks are used for a large volume secondary memory.
- a magnetic core memory comprises a matrix of ring-shaped ferromagnetic cores.
- Each memory cell of the magnetic core memory includes a ferromagnetic core having two or more wires passing through the center of the core and a sensing coil installed around the core.
- the magnetic induction B in the core has two states, B r and -B r , that correspond to the opposite directions of the magnetic field. Accordingly, each core can store a bit of binary data by associating one state with a "1" and the other state with a "0". Illustratively, +B r may be associated with a binary "1" and -B r with a binary "0".
- the binary data is written into a core memory cell by applying appropriate currents to the wires. If the total current passing through the core is greater than a critical current I c , the magnetic induction of the core changes from -B r to +B r . Similarly, if the current is less than -I c , the magnetic induction switches from +B r to -B r .
- switching is performed as the result of the coincidence of signals on two or more wires.
- the data stored in the core is retrieved by sensing the voltage across the coil induced by switching between the two magnetic states described above.
- the polarity of the induced voltage indicates the magnetic state of the core prior to switching.
- a magnetic thin film memory consists of a strip of ferromagnetic thin film, two or more wires for writing data formed on the film and a coil around the film for reading data.
- the magnetic moment M of the film represents the stored information.
- the magnetic moment M is oriented primarily in the plane of the film, and has two discrete orientations or states M and -M that represent binary "1" and "0".
- currents are applied to the wires formed on the thin film. These currents induce a magnetic field that is sufficient for changing the direction of the magnetic moment M.
- the stored information is retrieved by applying currents to the wires and measuring the induced voltage in the coil.
- the currents are typically selected such that a single current has insufficient amplitude to reverse the magnetic moment of the film so that at least two coincident currents are required for storing data.
- thin film devices have an open magnetic flux structure and therefore the BH loop is smeared by a self-demagnetizing effect.
- the film is typically fabricated as a rectangle whose length is much greater than its width. Since the induced voltage in the coil around the film is proportional to the cross-sectional area of the film, reducing the width of the film also reduces the induced voltage. As a result, the readout signal is easily affected by noise.
- the magnetic moment has a preferred in-plane direction.
- the device is complicated by the necessity of applying currents of different amplitude for storing and retrieving data in the selected orientations.
- the thin film devices are not sufficiently small to achieve high densities.
- DRAM Dynamic Random Access Memory
- SRAM Static Random Access Memory
- ROM Read Only Memory
- DRAM offers relatively high speed, high density, low power consumption, and is readable and writable.
- both DRAM and SRAM are volatile, that is, they lose the stored information when the power is turned off.
- DRAM requires a constant refresh of the stored data which necessitates complex circuitry.
- SRAM does not require a refresh, it has high power consumption and does not have high storage density.
- ROM's are non-volatile but the information stored in a ROM cannot be updated, i.e., data cannot be easily written into a ROM.
- ferromagnetic material having a substantially square BH loop is coated on the disk; and a magnetic head reads and writes information on the disk as it rotates past the head.
- the disk is divided into circular tracks. Each track is further divided into small regions in which a magnetic moment has two states that represent binary values.
- An external magnetic field introduced by the read/write head changes the magnetic moment of each small region so as to store a binary value in the region.
- the magnetic head magnetizes an adjacent small region of the rotating disk material. Stored data is retrieved in the form of a voltage induced in the head by the magnetic moment of the small region as it moves past the head.
- Magnetic disk storage systems can store high volumes of data, e.g., 500 Megabytes or more.
- the magnetic disk storage systems are not random accessible, operate at slow speed due to the requirement of mechanical movement, and require complex mechanical and electronic assemblies.
- the present invention relates to a new composition of materials which has ferromagnetic, piezoelectric and electro-optical properties and can be employed as a storage media.
- This invention also relates to a non-volatile random accessible memory built on the basis of the invented composition of materials.
- a novel method for storing and retrieving two independent bits of information in a single memory cell of the present invention is also disclosed.
- the preferred composition of materials of the present invention comprises layers of Pb.sub.(1-x-y) Cd x Si y , Se.sub.(1-z) S z , and Fe.sub.(1-w) Cr w where x, y, z and w indicate the proportions of the elements within their respective layers. These values are preferably within the following ranges: 0.09 ⁇ x ⁇ 0.11, 0.09 ⁇ y ⁇ 0.11, 0.09 ⁇ z ⁇ 0.11, and 0.22 ⁇ w ⁇ 0.36.
- the layers of the composition of materials also contain the following elements: Bi, Ag, O and N. These elements are introduced by electrolysis in a solution containing Bi 2 O 3 and AgNO 3 .
- two sets of parallel address lines are disposed orthogonally on the opposite sides of a planar substrate.
- the layers of the novel composition of materials, as described above, are disposed on both sides of the substrate above the address lines with the FeCr layers outermost, and an electrode is connected to the outermost FeCr layer on each side of the substrate.
- An individual memory cell is located at each crossing point of the address lines of the two sets.
- two synchronized current pulses having the same amplitude and polarity are applied to two orthogonal address lines.
- the second bit is stored and retrieved in that memory cell by applying two synchronized pulses of the same amplitude but opposite polarity to the same two address lines.
- the current pulses employed for storing binary information are such that the amplitude of a single pulse is not sufficient to alter the state of the stored information but that two concurrent pulses are sufficient for storing data.
- the current pulses employed for retrieving the stored binary information have amplitudes insufficient to alter the stored information.
- Such a memory cell is non-volatile, random accessible, static, operates at high speed, requires low power, is readable and writable, and can be made in high density arrays.
- FIG. 1 shows the cross-section of a preferred embodiment of the composition of materials of the present invention
- FIG. 2 illustrates the magnetization curve (BH loop) of a conventional ferromagnetic material
- FIG. 3 shows a substantially square BH loop of the composition of materials of the present invention
- FIGS. 4(a)-4(j) illustrate the process of generating piezoelectric voltage within the composition of materials
- FIGS. 5(a) and 5(b) are the cross section and top-view of the preferred embodiment of the memory device of the invention.
- FIGS. 6(a) and 6(b) illustrate the process of selecting carriers within the memory device
- FIGS. 7(a) and 7(b) illustrate storing the first bit of information into the memory device
- FIGS. 8(a) and 8(b) show the process of reading the stored first bit of information
- FIGS. 9(a) and 9(b) illustrate storing a second bit of information into the memory device
- FIG. 10 shows the current pulses used for retrieving the second bit of information stored in the memory device and corresponding output
- FIG. 11 is a summary list of preferred methods for storing and retrieving information from the memory device.
- FIGS. 12(a) and 12(b) show the electrical current with respect to process time in an electrolysis process utilized as a step in fabricating the composition of materials.
- the present invention relates to a composition of materials having ferromagnetic, electro-optic and piezoelectric properties.
- a random accessible non-volatile memory device utilizing the invented composition of materials is also disclosed.
- the memory device is capable of storing two independent bits of information.
- the preferred composition of materials comprises layers of Pb.sub.(1-x-y) Cd x Si y , Se.sub.(1-z) S z , and Fe.sub.(1-w) Cr w .
- the values of x, y, z and w are preferably in the ranges of 0.09 ⁇ x ⁇ 0.11, 0.09 ⁇ y ⁇ 0.11, 0.09 ⁇ z ⁇ 0.11, and 0.22 ⁇ w ⁇ 0.26.
- each layer also includes one or more of the elements Bi, Ag, O and N.
- Ge can be employed in place of Si and/or Zn or Te can be employed in place of Pb.
- other conductive elements such as Au, Pt, or Cu can be added to the layer structure in place of Ag.
- the invention may also be practiced using concentrations of Cr in the Fe.sub.(1-w) Cr w layer such that w ranges from 0.18 to 0.30.
- a preferred embodiment of the invented composition of materials comprises a Pb 0 .80 Cd 0 .10 Si 0 .10 layer 110, a Se 0 .90 S 0 .10 layer 120, and a Fe 0 .76 Cr 0 .24 layer 130.
- the Fe 0 .76 Cr 0 .24 layer is mainly responsible for the ferromagnetic properties of the composition of materials, and the Pd 0 .80 Cd 0 .10 Si 0 .1 and Se 0 .9 S 0 .1 layers are mainly responsible for its electro-optical properties. All three layers exhibit piezoelectric properties.
- each of the Pb 0 .80 Cd 0 .10 Si 0 .10, Se 0 .90 S 0 .10 and Fe 0 .76 Cr 0 .24 layers is 0.5 ⁇ m thick.
- a ferromagnetic material exhibits a permanent magnetic field in the absence of an external magnetic field.
- Such materials can be described in terms of a large number of small magnets known as magnetic dipoles.
- An external magnetic field applied to a ferromagnetic material aligns the magnetic dipoles within the material in the direction of the applied field, so that the total magnetic field within the material is the sum of the external field and the field generated by the aligned magnetic dipoles.
- the orientation of magnetic dipoles does not change, resulting in a constant magnetic field in the material.
- Magnetic information storage is based on this property of ferromagnetic materials.
- FIG. 2 shows an exemplary magnetization curve of a typical ferromagnetic material.
- the magnetization curve is also referred to as a BH loop.
- the y axis in this figure represents magnetic induction B, which is the overall magnetic field in the material, and the x axis represents the magnetic field strength H of the external magnetic field.
- the BH loop shows the change in the magnetic induction B with changing magnetic field strength H.
- FIG. 3 illustrates the BH loop of the composition of materials of the present invention.
- the x-axis indicates the external field strength H and the y axis indicates the magnetic induction B.
- the composition of materials of the present invention also has piezoelectric properties.
- a piezoelectric voltage is generated.
- the mechanical pressure on the composition of materials is reduced in a direction substantially perpendicular to the plane of the layers within the composition of materials, a piezoelectric voltage is generated across the layers.
- the change in mechanical pressure is produced by a change in the magnetic states of the composition of materials.
- FIG. 4(a) An illustrative structure exhibiting the piezoelectric properties of the present invention is shown in FIG. 4(a). An explanation of its operation is set forth in conjunction with FIGS. 4(b)-4(j).
- FIG. 4(a) illustrates a structure 190 comprising two layers of the composition of materials of the present invention.
- the structure comprises a first FeCr layer 200, a first SeS layer 210, a first PbCdSi layer 220, a second PbCdSi layer 230, a second SeS layer 240, and a second FeCr layer 250.
- a wire 260 passes through the middle of the structure, parallel to the layers.
- an electrical current applied to the wire 260 in a direction that is into the page generates a substantially circular magnetic field around the wire, as indicated by a circle B r in the clockwise direction indicated by the arrow.
- Arrows 270 illustrate the directions of the magnetic dipoles in FeCr layers 200, 250 under the influence of this external field.
- the dipole arrangement in sections 275, 280 is equivalent to two magnets of the same strength having north and south poles as indicated by arrows 282 and 284 in FIG. 4(c).
- the length of each arrow represents the amplitude of the magnetic induction B of the corresponding magnet. Due to the attraction between the South pole S and the North pole N of each magnet, the storage media is mechanically compressed in the direction perpendicular to the layers of the structure.
- the BH loop of the magnetic induction B r is shown in FIG. 4(d). As described previously the BH loop is substantially square, exhibiting two discrete, stable magnetic states, +B 0 and -B 0 .
- the magnetic field has a critical field strength H c which is defined as the amplitude of the magnetic field strength which causes switching between +B 0 and -B 0 . Consequently, if H is greater than H c , the magnetic induction B r will have a value +B 0 . If H is less than -H c , B r will have a value -B 0 .
- FIG. 4(f) shows that at point “f" the poles of the magnets have been reversed.
- the mechanical pressure on the layer returns to its initial value, diminishing the piezoelectric voltage.
- Increasing the reversed current further would not increase the magnitude of the dipole moment and therefore would not increase mechanical pressure on the layers.
- FIG. 4(g) illustrates the piezoelectric voltage that corresponds to various points on the BH loop of FIG. 4(d) as B 0 changes to -B 0 .
- the piezoelectric voltage generated in response to a current pulse is illustrated in the time domain.
- the piezoelectric voltage is a piezoelectric voltage pulse that is delayed from the time of the application of the current pulse.
- the current pulse applied to the wire has an amplitude -I that is sufficient to switch B 0 to -B 0 ,
- a current that generates a field having an amplitude greater than H c is required for switching between the magnetic states. If, however, a current is applied having a lesser amplitude which causes B to assume a value indicated by point "c" in FIG. 4(e), the magnetic state is unstable. In such case, the magnetic induction B tends to oscillate between the values of B 0 (point "b") and B c (point "c").
- a piezoelectric voltage pulse generated in response to such oscillation is shown in FIG. 4(i). The amplitude V 2 of this piezoelectric voltage pulse is smaller than the amplitude of the pulse generated as a result of switching from +B 0 to -B 0 (FIG. 4(g)).
- FIG. 4(j) shows a current pulse I which causes B to assume the value B c .
- the piezoelectric voltage pulse, generated in response to this current is shown in the lower portion of the figure.
- the shaded area reflects the oscillation between the two states (B c and +B 0 ), as it would be observed on an oscilloscope.
- the piezoelectric voltage generated in response to the current that disturbs but does not switch the magnetic states can be employed for reading magnetically stored information.
- FIGS. 5(a) and 5(b) illustrate the cross-section (not to scale) and the top-view of a preferred embodiment of a portion of a memory device 290 of the present invention.
- the memory device comprises a silicon planar substrate 330, first address lines 320 formed on one surface of the substrate, and second address lines 340 orthogonal to the first lines, formed on the opposite surface of the substrate.
- a first set 310 and a second set 350 of the layers of materials of the present invention are disposed on opposite sides of the substrate over the address lines.
- Electrodes 300, 360 are connected to the layers 310, 350 respectively of the composition of materials.
- the first and second address lines are silver strips approximately 2 ⁇ m wide and approximately 1 ⁇ m thick.
- the spacing between adjacent address lines is approximately between 9 to 20 ⁇ m, depending on the desired density of the memory device. For example in one embodiment the spacing is 9.5 ⁇ m and in a different embodiment the spacing is 19 ⁇ m.
- Each set of layers of materials 310, 350 comprise a Pb 0 .80 Cd 0 .10 Si 0 .1 layer, a Se 0 .90 S 0 .10 layer, and a Fe 0 .76 Cr 0 .24 layer sequentially formed on one of the address lines 320, 340 on the Si substrate with the two FeCr layers being outermost.
- each of the layers is preferably 0.5 ⁇ m thick so that each set is preferably 1.5 ⁇ m.
- Each layer is homogeneously saturated with Bi, Ag, O, and N.
- the substrate is 40 ⁇ m thick and the electrodes are 1 ⁇ m thick silver layers.
- the fabrication of this device begins with depositing 1 ⁇ m thick metal (preferably silver) layers onto the opposite surfaces of a 40 ⁇ m thick silicon planar substrate.
- metal preferably silver
- substrates made of other materials such as BaF 2 could be used in place of the Si substrate.
- the deposition is conducted by a conventional technique such as thermal evaporation, e-beam evaporation, or sputtering.
- the deposited silver layers are then photolithographically patterned and etched to form a series of metal strips, each having a width of approximately 2 ⁇ m.
- the series of strips on one side of the Si substrate is orthogonal to the strips on the opposite side.
- the strips on both sides of the substrate form a cross-barred structure.
- the layers of Pb 0 .80 Cd 0 .10 Si 0 .10, Se 0 .90 S 0 .10, and Fe 0 .76 Cr 0 .24 are then deposited sequentially.
- components of the layers Prior to the deposition, components of the layers are prepared by mixing together proper amounts of powder of each required element.
- the amount of powder of each element corresponds to the desired proportion of the element in the corresponding layer.
- layer the powders of Pb, Cd and Si are mixed in the proportions 80:10:10.
- the source materials for deposit of the Se 0 .90 S 0 .10 and Fe 0 .76 Cr 0 .24 layers are prepared in a similar fashion.
- the layers of Pb 0 .80 Cd 0 .10 Si 0 .10, Se 0 .9 S 0 .1 and Fe 0 .76 Cr 0 .24 are then sequentially deposited onto both sides of the substrate.
- the deposition can be accomplished using well-known methods. For example in the preferred embodiment a plasma sputtering techniques is utilized for creating the layered structure. After each layer is deposited by sputtering, the temperature of the layer is raised rapidly (i.e. in about 1.5 seconds) to approximately 500° C. and then cooled to approximately a room temperature for the deposition of the next layer. As conventionally done, the spattering is performed in vacuum utilizing Ar gas.
- each of the Pb 0 .80 Cd 0 .10 Si 0 .10, Se 0 .90 S 0 .10, and Fe 0 .76 Cr 0 .24 layers is approximately 0.5 ⁇ m thick, forming two structures approximately 1.5 ⁇ m thick on the opposite surfaces of the substrate with the two FeCr layers being outermost.
- the elements Bi, Ag, O and N by are then added to the layers by an electrolysis process that employs a heated electrolyte containing Bi 2 O 3 and AgNO 3 .
- the electrolyte is prepared by heating high purity water to 97° C. in a stainless steel container with a stirring device on the bottom of the container.
- the Bi 2 O 3 and AgNO 3 powders are then added to the heated water to form the electrolyte.
- the proportion of weight of the added powders is about 40% of Bi 2 O 3 and 60% of AgNO 3 .
- the amounts of these powders can be adjusted to achieve a desired current in the electrolyte.
- the electrolyte is maintained at 97° C. and stirred continuously for at least one hour to form a uniform solution.
- the metal strips on both sides of the substrate Prior to the electrolysis process, all the metal strips on both sides of the substrate are connected to form a single electrode.
- the substrate is then immersed in the electrolyte which is maintained at a temperature of 97° C. and is continuously stirred.
- many substrates can be simultaneously immersed in the electrolysis solution. For example, 100 1 cm ⁇ 1 cm substrates can be processed simultaneously. In this case the metal strips of all the substrates should be connected to a single electrode.
- the complete electrolysis process takes 45 days. Each day the same process cycle is repeated. During the initial 10 hours of the cycle, an electrical potential of +60 V is applied to the substrates and during the next 14 hours, a -60 V potential is applied to the substrates.
- the stainless steel container is always kept at ground potential. Also, every 12 hours during the electrolysis process, the positions of the substrates within the container are interchanged for uniform processing. Throughout the process the electrolyte is continuously stirred.
- FIG. 12(a) illustrates the current I in Amperes in the electrolyte during the first forty days of the process. The days are indicated on the horizontal axis "t".
- FIG. 12(b) illustrates the values of the current I during the last five days. The current I is in mA's.
- the electrode is disconnected from the substrates and the substrates are removed from the electrolyte solution.
- the ions of the elements listed above have sufficiently penetrated the layered structure. Note that in a different embodiment ion implantation techniques can be employed for introducing these elements into the layered structure.
- composition of materials on both surfaces of the substrate is then polished until the surfaces are substantially smooth. Subsequently, an approximately 1 ⁇ m thick layer of silver is deposited on the surfaces of each substrate to form the electrodes 300, 360.
- the set of metal strips on the lower surface of the Si substrate forms a first set of addressing lines, (referred to as X lines), and the set of metal strips on the upper surface of the substrate forms a second set of addressing lines, (referred to as Y lines).
- X lines first set of addressing lines
- Y lines second set of addressing lines
- FIGS. 6(a) and 6(b) show top views of a single cell of the memory device.
- the orthogonal address lines 325, 345 divide the cell into four quarters 370, 375, 380 and 385, as illustrated in FIG. 6(a).
- a first bit of information is magnetically stored in the quarters 370 and 380 and a second bit is magnetically stored in the quarters 375 and 385.
- the quarters 370 and 380, where a first bit of information is stored are collectively referred to as carrier "a" and the quarters 375 and 385 where a second bit is stored are collectively referred to as a carrier "b".
- two electrical currents having specified amplitudes and polarities are applied to the first and second address lines, 325, 345.
- Information is retrieved from one of the carriers by applying two electrical currents to the address lines and measuring a piezoelectric voltage generated between the upper and lower electrodes.
- the current applied to the first address line is represented as I i
- the current applied to the second address line is represented as I j .
- the directions of I i and I j are indicated by the arrows entering the address lines.
- the currents I i and I j have the same amplitude, I 0 .
- Each current generates an induced circular magnetic field around the address lines as illustrated by the arrows 390 and 395.
- FIGS. 6(a) and 6(b) The directions of the magnetic fields B i and B j induced by I i and I j in each quarter is illustrated in FIGS. 6(a) and 6(b).
- a dot (•) indicates that the field is in the "up” direction and a cross (x) indicates that the field is in the opposite or "down” direction.
- B i and B j have the opposite directions and thus cancel each other out. For this reason the currents illustrated in FIG. 6(a) do not affect the information stored in the carrier "b".
- the fields B i and B j are induced in the same direction. Accordingly, these fields enhance each other and, thus, can alter the stored information.
- FIG. 6(b) illustrates the process of selecting the carrier "b".
- the fields generated by these currents cancel each other out, without affecting the magnetic state.
- carrier "b” however the fields generated by these currents enhance each other so that the carrier "b” is selected.
- the amplitudes of the two currents combined should be sufficiently large to switch the magnetization of a carrier between the magnetic states B 0 and -B 0 .
- the amplitudes of the two currents combined should be sufficiently small so that a single current alone is unable to change the magnetic state of a carrier. This is necessary to assure that only one carrier in the memory array is selected by the signal on an address line.
- the amplitudes of the two currents combined should be small enough that the induced field is not strong enough to change the magnetic state of the carrier.
- the combined amplitudes should be sufficient to disturb the magnetic state of the carrier so as to generate a piezoelectric voltage across the storage media. As discussed above, the direction of this piezoelectric voltage represents the binary data stored in the carrier.
- FIG. 7(a) depicts the process of writing a binary "1" into the carrier "a” using synchronous current pulses on the two address lines.
- all the cells of the array are assumed to be in the "0" state which corresponds to a magnetic induction of -B 0 .
- This generates a magnetic field H which magnetizes the FeCr layers of the composite material.
- the magnetic induction B a of these layers is depicted in FIG. 7(a) as a closed loop with an arrow.
- the amplitude of the critical current I c necessary to generate the critical field strength H c required for switching between the two discrete states is approximately 35 ⁇ A.
- the two +20 ⁇ A currents create a field H that would be generated by applying a 40 ⁇ A current. Since this current is greater than I c , the magnetic induction becomes B 0 so that a binary "1" is stored.
- the magnetic induction at the cell B a remains equal to B o , so that a binary "1" is retained in the carrier "a".
- Switching between +B 0 and -B 0 generates a piezoelectric voltage pulse between the first and second electrodes after a delay ⁇ t from the time of the application of the current pulses.
- the piezoelectric pulse is positive for switching from +B 0 to -B 0 and is negative for switching from -B 0 to +B 0 . If the magnetic state does not change, no piezoelectric pulse is generated. Accordingly, the generated piezoelectric voltage pulses can be employed to verify that a bit of binary data has been stored.
- This process of retrieving data is illustrated in the time domain in FIG. 8(b).
- the delay between the piezoelectric voltage pulse and the synchronized current pulses is approximately 0.75 ns.
- the data stored in the carrier "b” is retrieved in a similar way as discussed in conjunction with carrier "a”.
- FIG. 11 summarizes the above-described methods of storing and retrieving data from the carriers "a" and "b" of the memory device.
- a method of destructive readout can also be employed.
- One of the advantages of the memory device of the present invention is its low power consumption as compared with the prior art non-volatile magnetic memory devices. Since the storage media employed in this device is highly sensitive to the magnetic field generated by the driving currents, it can quickly switch between "0" and "1" at relatively small driving currents, about 20 ⁇ A on each line. Consequently, the power consumption is low for storing and retrieving data. In one embodiment, it consumes approximately 3.4 ⁇ 10 -10 w for reading and 6 ⁇ 10 -10 w for storing a bit of data into the device.
- the delay between the current pulses and corresponding piezoelectric voltage is in the range of subnanoseconds. Switching between "1" and “0” usually takes a few nanoseconds.
- This memory device which is random accessible, non-volatile, and operates in static mode has been described.
- This memory device offers high-speed operation, low power consumption, and can store information at high density.
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Priority Applications (13)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/889,025 US5390142A (en) | 1992-05-26 | 1992-05-26 | Memory material and method for its manufacture |
AT93914174T ATE304733T1 (de) | 1992-05-26 | 1993-05-26 | Speichermaterial und verfahren zur herstellung |
KR1019950705292A KR100300771B1 (ko) | 1992-05-26 | 1993-05-26 | 메모리용합성물및그제조방법 |
PCT/US1993/005011 WO1994028552A1 (en) | 1992-05-26 | 1993-05-26 | Memory material and method for its manufacture |
EP93914174A EP0700571B1 (de) | 1992-05-26 | 1993-05-26 | Speichermaterial und verfahren zur herstellung |
JP50056995A JP3392869B2 (ja) | 1992-05-26 | 1993-05-26 | メモリ材料及びその製造方法 |
DE69333869T DE69333869D1 (de) | 1992-05-26 | 1993-05-26 | Speichermaterial und verfahren zur herstellung |
AU43930/93A AU4393093A (en) | 1992-05-26 | 1993-05-26 | Memory material and method for its manufacture |
CA002163739A CA2163739C (en) | 1992-05-26 | 1993-05-26 | Memory material and method for its manufacture |
RU95122718/25A RU2124765C1 (ru) | 1992-05-26 | 1993-05-26 | Композиция материала запоминающего устройства, способ его изготовления, энергонезависимое запоминающее устройство, способ его изготовления, способ запоминания и воспроизведения двух независимых бит двоичных данных в одной ячейке памяти энергонезависимого запоминающего устройства |
US08/486,790 US5602791A (en) | 1992-05-26 | 1995-06-07 | Memory material and method of its manufacture |
US08/797,086 US5717235A (en) | 1992-05-26 | 1997-02-10 | Non-volatile memory device having ferromagnetic and piezoelectric properties |
US08/797,087 US5707887A (en) | 1992-05-26 | 1997-02-10 | Method of manufacturing a non-volatile random accessible memory device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US07/889,025 US5390142A (en) | 1992-05-26 | 1992-05-26 | Memory material and method for its manufacture |
PCT/US1993/005011 WO1994028552A1 (en) | 1992-05-26 | 1993-05-26 | Memory material and method for its manufacture |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US38497295A Division | 1992-05-26 | 1995-02-07 |
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Publication Number | Publication Date |
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US5390142A true US5390142A (en) | 1995-02-14 |
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ID=25394375
Family Applications (4)
Application Number | Title | Priority Date | Filing Date |
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US08/486,790 Expired - Fee Related US5602791A (en) | 1992-05-26 | 1995-06-07 | Memory material and method of its manufacture |
US08/797,087 Expired - Fee Related US5707887A (en) | 1992-05-26 | 1997-02-10 | Method of manufacturing a non-volatile random accessible memory device |
US08/797,086 Expired - Fee Related US5717235A (en) | 1992-05-26 | 1997-02-10 | Non-volatile memory device having ferromagnetic and piezoelectric properties |
Family Applications After (3)
Application Number | Title | Priority Date | Filing Date |
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US08/486,790 Expired - Fee Related US5602791A (en) | 1992-05-26 | 1995-06-07 | Memory material and method of its manufacture |
US08/797,087 Expired - Fee Related US5707887A (en) | 1992-05-26 | 1997-02-10 | Method of manufacturing a non-volatile random accessible memory device |
US08/797,086 Expired - Fee Related US5717235A (en) | 1992-05-26 | 1997-02-10 | Non-volatile memory device having ferromagnetic and piezoelectric properties |
Country Status (10)
Country | Link |
---|---|
US (4) | US5390142A (de) |
EP (1) | EP0700571B1 (de) |
JP (1) | JP3392869B2 (de) |
KR (1) | KR100300771B1 (de) |
AT (1) | ATE304733T1 (de) |
AU (1) | AU4393093A (de) |
CA (1) | CA2163739C (de) |
DE (1) | DE69333869D1 (de) |
RU (1) | RU2124765C1 (de) |
WO (1) | WO1994028552A1 (de) |
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US5524092A (en) * | 1995-02-17 | 1996-06-04 | Park; Jea K. | Multilayered ferroelectric-semiconductor memory-device |
US5602791A (en) * | 1992-05-26 | 1997-02-11 | Kappa Numerics, Inc. | Memory material and method of its manufacture |
US5673220A (en) * | 1992-10-30 | 1997-09-30 | Kappa Numerics, Inc. | Memory material and method for its manufacture |
US5757056A (en) * | 1996-11-12 | 1998-05-26 | University Of Delaware | Multiple magnetic tunnel structures |
US5841689A (en) * | 1996-11-29 | 1998-11-24 | Gendlin; Shimon | Non-volatile record carrier with magnetic quantum-optical reading effect and method for its manufacture |
US6153318A (en) * | 1996-04-30 | 2000-11-28 | Rothberg; Gerald M. | Layered material having properties that are variable by an applied electric field |
EP1318523A1 (de) * | 2001-12-05 | 2003-06-11 | Korea Advanced Institute of Science and Technology | Verfahren zum Steuer der Easy-axis-magnetisierung in ferromagnetische Films mit Spannung, ultrahoche Dichte nicht-flüchtiger magnetische Speicher für geringe Spannungen mit diesem Verfahren hergestellte und Verfahren zum Schreiben von Daten in diese Speicher |
US6835463B2 (en) | 2002-04-18 | 2004-12-28 | Oakland University | Magnetoelectric multilayer composites for field conversion |
US20080024910A1 (en) * | 2006-07-25 | 2008-01-31 | Seagate Technology Llc | Electric field assisted writing using a multiferroic recording media |
US20110002107A1 (en) * | 2008-02-22 | 2011-01-06 | Junsuke Tanaka | Transponder and Booklet |
US20130180101A1 (en) * | 1999-10-23 | 2013-07-18 | Ultracard, Inc. | Data Storage Device, Apparatus And Method For Using Same |
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NO309500B1 (no) * | 1997-08-15 | 2001-02-05 | Thin Film Electronics Asa | Ferroelektrisk databehandlingsinnretning, fremgangsmåter til dens fremstilling og utlesing, samt bruk av samme |
US6104633A (en) * | 1998-02-10 | 2000-08-15 | International Business Machines Corporation | Intentional asymmetry imposed during fabrication and/or access of magnetic tunnel junction devices |
US6548843B2 (en) * | 1998-11-12 | 2003-04-15 | International Business Machines Corporation | Ferroelectric storage read-write memory |
NO20041733L (no) * | 2004-04-28 | 2005-10-31 | Thin Film Electronics Asa | Organisk elektronisk krets med funksjonelt mellomsjikt og fremgangsmate til dens fremstilling. |
US7579197B1 (en) * | 2008-03-04 | 2009-08-25 | Qualcomm Incorporated | Method of forming a magnetic tunnel junction structure |
US8634231B2 (en) | 2009-08-24 | 2014-01-21 | Qualcomm Incorporated | Magnetic tunnel junction structure |
RU2468471C1 (ru) * | 2011-04-07 | 2012-11-27 | Государственное образовательное учреждение высшего профессионального образования "Петрозаводский государственный университет" | Способ получения энергонезависимого элемента памяти |
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- 1993-05-26 JP JP50056995A patent/JP3392869B2/ja not_active Expired - Fee Related
- 1993-05-26 EP EP93914174A patent/EP0700571B1/de not_active Expired - Lifetime
- 1993-05-26 AT AT93914174T patent/ATE304733T1/de not_active IP Right Cessation
- 1993-05-26 RU RU95122718/25A patent/RU2124765C1/ru not_active IP Right Cessation
- 1993-05-26 KR KR1019950705292A patent/KR100300771B1/ko not_active IP Right Cessation
- 1993-05-26 DE DE69333869T patent/DE69333869D1/de not_active Expired - Lifetime
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Cited By (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5602791A (en) * | 1992-05-26 | 1997-02-11 | Kappa Numerics, Inc. | Memory material and method of its manufacture |
US5673220A (en) * | 1992-10-30 | 1997-09-30 | Kappa Numerics, Inc. | Memory material and method for its manufacture |
US5524092A (en) * | 1995-02-17 | 1996-06-04 | Park; Jea K. | Multilayered ferroelectric-semiconductor memory-device |
US6153318A (en) * | 1996-04-30 | 2000-11-28 | Rothberg; Gerald M. | Layered material having properties that are variable by an applied electric field |
US6413659B1 (en) | 1996-04-30 | 2002-07-02 | Gerald M. Rothberg | Layered material having properties that are variable by an applied electric field |
WO1998024163A2 (en) * | 1996-11-12 | 1998-06-04 | Chui Siu Tat | Multiple magnetic tunnel structures |
WO1998024163A3 (en) * | 1996-11-12 | 1998-10-08 | Chui Siu Tat | Multiple magnetic tunnel structures |
US5757056A (en) * | 1996-11-12 | 1998-05-26 | University Of Delaware | Multiple magnetic tunnel structures |
US5841689A (en) * | 1996-11-29 | 1998-11-24 | Gendlin; Shimon | Non-volatile record carrier with magnetic quantum-optical reading effect and method for its manufacture |
US9430727B2 (en) * | 1999-10-23 | 2016-08-30 | Ultracard, Inc. | Data storage device, apparatus and method for using same |
US20130180101A1 (en) * | 1999-10-23 | 2013-07-18 | Ultracard, Inc. | Data Storage Device, Apparatus And Method For Using Same |
EP1318523A1 (de) * | 2001-12-05 | 2003-06-11 | Korea Advanced Institute of Science and Technology | Verfahren zum Steuer der Easy-axis-magnetisierung in ferromagnetische Films mit Spannung, ultrahoche Dichte nicht-flüchtiger magnetische Speicher für geringe Spannungen mit diesem Verfahren hergestellte und Verfahren zum Schreiben von Daten in diese Speicher |
US7201817B2 (en) | 2002-04-18 | 2007-04-10 | Oakland University | Magnetoelectric multilayer composites for field conversion |
US20050104474A1 (en) * | 2002-04-18 | 2005-05-19 | Oakland University | Magnetoelectric multilayer composites for field conversion |
US6835463B2 (en) | 2002-04-18 | 2004-12-28 | Oakland University | Magnetoelectric multilayer composites for field conversion |
US20080024910A1 (en) * | 2006-07-25 | 2008-01-31 | Seagate Technology Llc | Electric field assisted writing using a multiferroic recording media |
US7706103B2 (en) * | 2006-07-25 | 2010-04-27 | Seagate Technology Llc | Electric field assisted writing using a multiferroic recording media |
US20110002107A1 (en) * | 2008-02-22 | 2011-01-06 | Junsuke Tanaka | Transponder and Booklet |
US9934459B2 (en) * | 2008-02-22 | 2018-04-03 | Toppan Printing Co., Ltd. | Transponder and booklet |
Also Published As
Publication number | Publication date |
---|---|
JPH08510867A (ja) | 1996-11-12 |
US5707887A (en) | 1998-01-13 |
EP0700571A1 (de) | 1996-03-13 |
CA2163739A1 (en) | 1994-12-08 |
JP3392869B2 (ja) | 2003-03-31 |
KR960702666A (ko) | 1996-04-27 |
RU2124765C1 (ru) | 1999-01-10 |
WO1994028552A1 (en) | 1994-12-08 |
US5602791A (en) | 1997-02-11 |
EP0700571B1 (de) | 2005-09-14 |
ATE304733T1 (de) | 2005-09-15 |
AU4393093A (en) | 1994-12-20 |
DE69333869D1 (de) | 2005-10-20 |
US5717235A (en) | 1998-02-10 |
CA2163739C (en) | 2002-04-02 |
EP0700571A4 (de) | 1997-10-22 |
KR100300771B1 (ko) | 2001-10-22 |
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